Renal insufficiency, especially, acute renal insufficiency is such a serious disease that waste materials are accumulated in the blood owing to the deficiency of the renal function, and the development of an agent for preventing, curing or treating the renal insufficiency has been in demand. It is required to elucidate the renal function and to develope an appropriate treatment of the renal functional insufficiency.
It has been long known that xanthines such as caffeine, theophylline and the like possess diuretic activity. In recent years, studies have been made with respect to the diuretic activity of these xanthines, and it has been clarified that the xanthines act as an antagonist of an adenosine receptor. Further, in recent years, it has been discovered that 8-(3-noradamantyl)-1,3-dipropylxanthine (hereinafter sometimes referred to as "KW-3902") exhibits an excellent adenosine receptor antagonizing activity, and this compound has been developed as a medicine having an antihypertensive activity, a diuretic activity and kidney-protecting activity (F. Suzuki et al., J. Med. Chem., 35, 3066 (1992)). KW-3902 has attracted attention as a medicine which is especially effective for treating acute renal insufficiency. This KW-3902 is deemed effective in the parenteral administration. KW-3902 is sparingly soluble in water, and it is difficult to produce its preparations. In addition, the compound is problematic in a long-term storage stability. Thus, the development thereof as a medicine has posed a serious problem.
Meanwhile, a fat emulsion (lipid microsphere) has been already clinically applied for feeding, and also studies to apply the fat emulsion to preparation of an antiinflammatory antalgic agent have been conducted (Mizushima et al., "SAISHIN IGAKU", vol. 40, No. 9, pp. 1806-1813, 1985). However, medical ingredients which can be formulated with a fat emulsions are limited, and there have been problems that the stability thereof or the absorption of active ingredients varies depending on the ingredients, the amount, the physical form and the like of the fat emulsion.